Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $247.76   5.162%   $260.5494   $260.55   $260.55   $260.50  
  Purchase #2 $186.41   11.185%   $207.26   $207.26   $207.25   $207.30  
  Purchase #3 $130.79   11.735%   $146.1382   $146.14   $146.15   $146.10  
  Purchase #4 $216.56   3.836%   $224.8672   $224.87   $224.85   $224.90  
  Purchase #5 $172.46   6.860%   $184.2908   $184.29   $184.30   $184.30  
  Purchase #6 $134.79   7.325%   $144.6634   $144.66   $144.65   $144.70  
  Purchase #7 $203.31   6.865%   $217.2672   $217.27   $217.25   $217.30  
  7 purchase totals = $1,292.08       $1,385.0362   $1,385.04   $1,385.00   $1,385.10